Insulating bushing with flexible sheath mounting



INSULATING BUSHING WITH FLEXIBLE SHEATH MOUNTING' M. PEROLINI Filed March 17, 1948 Inventor: Marcel Peroiini,

His Attorney.

Patented Oct. 3, 1950 INSULATIN BUSHEN G WITH FLEXIBLE SHEATH MOUNTING Marcel Pcrolini, Paris, France, assignor to General Electric Company, a corporation of New York Application March 17, 1948, Serial No. 15,442 In France April 4, 1947 1 Claim.

This invention relates to insulating bushings and more particularly to insulating bushings for use with electric transformers and similar electrical apparatus.

The insulating bushings which are now gen erally used for the entrance of transformer or circuit breaker connections through the cover of such apparatus are subjected to mechanical stresses that are brought about by the internal and external connections, or that are caused either by the method of assembling the parts or bythe electrostatic stresses which appear in the case of short circuits. These stresses are of particularly great magnitude when high current circuits are involved.

In the insulating bushing of the conventional type of central conductor, the insulators, and the flanges for fastening the device form a system which is independent of the transformer cover. Therefore, the magnetic stresses set up within the bushing have to be withstood by the insulators alone; as a result these insulators which are often fabricated of a ceramic material such as porcelain, must be very strongly constructed.

This invention provides an insulating bushing construction which permits a substantial diminution of all mechanical stresses which tend to act upon the outer weather resistant insulators. This end is accomplished by separately mounting the conducting rod. which serves to bring the external electric connection into the electric apparatus and securing it to the wall (e. g.--a transformer tank cover) through which it passes. The insulator or insulators are secured, at one of their extremities, to the same wall and their other extremity is fastened, by means of an elastic sleeve and a hermetically tight joint to the conducting rod.

It is an object of this invention to provide an insulator bushing for use with electrical apparatus in which the magnetic stresses due to the construction of the bushing or the electrodynamic forces which occur upon short-circuit do not act on the frangible insulator.

The invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claim.

In the drawing Fig. 1 is a cross-sectional View of a transformer bushing constructed in accordance with this invention. Fig. 2 is a partial cross-sectional view of a similar transformer bushing illustrating an alternative construction of the invention. Fig. 3 is a cross-sectional view of a transformer bushing alsc showing an alternative construction of this invention. Fig. i is an enlarged view of a portion of Fig. 3.

Referring now to the drawing there is shown in Fig. l, by way of example, a bushing I which is mounted on a tank cover 2 of a transformer or circuit breaker or similar apparatus. The entrance bushing I has an external insulator 3 which is normally constructed of an insulating ceramic material such as porcelain. A conducting rod 4, which achieves the electrical connection between the external lead and the internal apparatus, passes within the external insulator 3 and through an aperture in the tank cover 2. The conducting rod 4 may be insulated by an impregnated paper coil or sheath 5, and at one end a metallic collar 6 is fitted on to the sheath 5 by hot shrinking or by a similar method of tight fitting. The collar 8 is threaded as is the transformer tank cover 2 to allow for the collar 6 being screwed into the cover 2. As is shown in Fig. l the threaded collar 6 is held rigidly on the conducting rod 4 and the insulating sheath 5 by means of an insulating tube 1 and a nut 8 which is screwed on t0 the lower end of the rod 4.

Fastened to the insulator 3 are two metallic collars 9 and Ill; 9 is at the lower end and II] at the upper end of the insulator 3. The lower collar 9 is fastened to the cover 2 by means of screws, bolts or other similar elements. A sealing joint or gasket II is inserted between the collar 9 and the cover 2 as shown in Fig. 1, and as the collar 9 is tightened down upon the cover 2 the sealing element I I is compressed thus preventing any leakage of dielectric fluid which may be within the bushing I. The upper collar I0 is fastened by means of screws, bolts or other similar elements to a flange I2 which is part of an elastic metallic joint I3. A sealing element I4 similar to seal II is inserted between the flange I2 and the insulator 3.

A flange I5 is pressed against a collar H which is mounted on the conducting rod 4 and is sep-- arated from it by a hermetically tight joint Iii. The compression of the gasket I6 is brought about by a nut I8 which is screwed on to the external end of the conducting rod 4.

It can be seen that the slight lateral displacements which follow stresses applied to the conducting rod 4, or the longitudinal displacements that are due to forces resulting from the expansion or contraction of the rod 4 are taken up by the expandable sleeve I3 and are transmitted only in a small degree to the frangible insulator 3 and to the elements by which it is secured.

It is apparent that the insulator 3 of the bushing I can be easily removed without affecting the conducting rod 4. Therefore, there is no need to unfasten the internal connections of the transformer or other electric apparatus from the conducting rod 4; this is particularly advantageous when dealing with large apparatus.

An alternative construction of this invention is shown in Fig. 2. In this construction the collar 6 is provided with a flange [9 which is bolted, or secured in any suitable fashion, to the transformer tank cover 2. A gasket 20 is inserted between the flange I9 and the cover 2. The lower collar 9 of the insulator 3 is bolted or similarly attached to the flange l9, and a hermetically tight joint 21 separates the flange I9 and the collar 9. This construction eliminates the necessity of threading the tank cover 2 and the corresponding collar 6, and thus eliminates the necessity of screwing in the conducting rod 4.

The alternative construction shown in Figs. 3 and 4 refers to a line entrance bushing 22 that comprises an external insulator 3 and an internal insulator 3. The collar 6 is fastened on to the insulating sheath of the conducting rod 4 by means of an arrangement similar to that shown in Fig. 1, in this case two insulating tubular spacing elements 1' and l which are rigidly positioned by the nuts 8 and 8. Nuts 8 and 8' are screwed on to the corresponding extremities of the conducting rod 4. The flange [9 on the collar (3 is secured by any appropriate means such as bolts to a metallic ring 23 which is fastened to the tank cover 2 by welding, bolting or some similar method. A gasket 20 separates the flange 19 from the ring 23. The insulators 3 and 3' are fastened to the flange l9 by means of the collars 9 and 9 and the gaskets 2| and 2|.

While there have been shown and described particular embodiments of this invention it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claim to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

A lead-in device for an electrical unit, said unit being enclosed in a container, said container having an aperture, said lead-in device comprising a conductive member extending from said unit through said aperture, an insulating sheath surrounding a portion of said conductive member and mounted thereon, a collar for rigidly securing said conductive member and said insulating sheath to said container, said collar having a flanged edge, a hollow frangible insulating bushing member mounted rigidly on said flanged edge and concentric to said conductive member, said hollow frangible insulating bushing member being constructed of a section external to said container and a section internal to said container, fluid-tight gasket members positioned between said hollow frangible insulating bushing member sections and said flanged edge, and fluidtight resilient joints coupling said conductive member to the extremities of said hollow frangible insulating bushing member sections for preventing the transmission of mechanical stresses from one to the other.

MARCEL PEROLINI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,777,073 Burnham Sept. 30, 1930 1,983,335 Austin Dec. 4, 1934 1,983,336 Austin Dec. 4, 1934 1,983,370 Hillebrand Dec. 4, 1934 2,099,581 Turner Nov. 16, 1937 2,135,321 Brandt Nov. 1, 1938 

